source: trunk/src/binutils/include/bfdlink.h@ 239

/* bfdlink.h -- header file for BFD link routines
   Copyright 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000
   Free Software Foundation, Inc.
   Written by Steve Chamberlain and Ian Lance Taylor, Cygnus Support.

This file is part of BFD, the Binary File Descriptor library.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

#ifndef BFDLINK_H
#define BFDLINK_H

/* Which symbols to strip during a link.  */
enum bfd_link_strip
{
  strip_none,           /* Don't strip any symbols.  */
  strip_debugger,       /* Strip debugging symbols.  */
  strip_some,           /* keep_hash is the list of symbols to keep.  */
  strip_all             /* Strip all symbols.  */
};

/* Which local symbols to discard during a link.  This is irrelevant
   if strip_all is used.  */
enum bfd_link_discard
{
  discard_none,         /* Don't discard any locals.  */
  discard_l,            /* Discard local temporary symbols.  */
  discard_all           /* Discard all locals.  */
};


/* These are the possible types of an entry in the BFD link hash
   table.  */

enum bfd_link_hash_type
{
  bfd_link_hash_new,            /* Symbol is new.  */
  bfd_link_hash_undefined,      /* Symbol seen before, but undefined.  */
  bfd_link_hash_undefweak,      /* Symbol is weak and undefined.  */
  bfd_link_hash_defined,        /* Symbol is defined.  */
  bfd_link_hash_defweak,        /* Symbol is weak and defined.  */
  bfd_link_hash_common,         /* Symbol is common.  */
  bfd_link_hash_indirect,       /* Symbol is an indirect link.  */
  bfd_link_hash_warning         /* Like indirect, but warn if referenced.  */
};

/* The linking routines use a hash table which uses this structure for
   its elements.  */

struct bfd_link_hash_entry
{
  /* Base hash table entry structure.  */
  struct bfd_hash_entry root;
  /* Type of this entry.  */
  enum bfd_link_hash_type type;

  /* Undefined and common symbols are kept in a linked list through
     this field.  This field is not in the union because that would
     force us to remove entries from the list when we changed their
     type, which would force the list to be doubly linked, which would
     waste more memory.  When an undefined or common symbol is
     created, it should be added to this list, the head of which is in
     the link hash table itself.  As symbols are defined, they need
     not be removed from the list; anything which reads the list must
     doublecheck the symbol type.

     Weak symbols are not kept on this list.

     Defined and defweak symbols use this field as a reference marker.
     If the field is not NULL, or this structure is the tail of the
     undefined symbol list, the symbol has been referenced.  If the
     symbol is undefined and becomes defined, this field will
     automatically be non-NULL since the symbol will have been on the
     undefined symbol list.  */
  struct bfd_link_hash_entry *next;
  /* A union of information depending upon the type.  */
  union
    {
      /* Nothing is kept for bfd_hash_new.  */
      /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
      struct
        {
          bfd *abfd;            /* BFD symbol was found in.  */
        } undef;
      /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
      struct
        {
          bfd_vma value;        /* Symbol value.  */
          asection *section;    /* Symbol section.  */
        } def;
      /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
      struct
        {
          struct bfd_link_hash_entry *link;     /* Real symbol.  */
          const char *warning;  /* Warning (bfd_link_hash_warning only).  */
        } i;
      /* bfd_link_hash_common.  */
      struct
        {
          /* The linker needs to know three things about common
             symbols: the size, the alignment, and the section in
             which the symbol should be placed.  We store the size
             here, and we allocate a small structure to hold the
             section and the alignment.  The alignment is stored as a
             power of two.  We don't store all the information
             directly because we don't want to increase the size of
             the union; this structure is a major space user in the
             linker.  */
          bfd_size_type size;   /* Common symbol size.  */
          struct bfd_link_hash_common_entry
            {
              unsigned int alignment_power;     /* Alignment.  */
              asection *section;                /* Symbol section.  */
            } *p;
        } c;
    } u;
};

/* This is the link hash table.  It is a derived class of
   bfd_hash_table.  */

struct bfd_link_hash_table
{
  /* The hash table itself.  */
  struct bfd_hash_table table;
  /* The back end which created this hash table.  This indicates the
     type of the entries in the hash table, which is sometimes
     important information when linking object files of different
     types together.  */
  const bfd_target *creator;
  /* A linked list of undefined and common symbols, linked through the
     next field in the bfd_link_hash_entry structure.  */
  struct bfd_link_hash_entry *undefs;
  /* Entries are added to the tail of the undefs list.  */
  struct bfd_link_hash_entry *undefs_tail;
};

/* Look up an entry in a link hash table.  If FOLLOW is true, this
   follows bfd_link_hash_indirect and bfd_link_hash_warning links to
   the real symbol.  */
extern struct bfd_link_hash_entry *bfd_link_hash_lookup
  PARAMS ((struct bfd_link_hash_table *, const char *, boolean create,
           boolean copy, boolean follow));

/* Look up an entry in the main linker hash table if the symbol might
   be wrapped.  This should only be used for references to an
   undefined symbol, not for definitions of a symbol.  */

extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
  PARAMS ((bfd *, struct bfd_link_info *, const char *, boolean, boolean,
           boolean));

/* Traverse a link hash table.  */
extern void bfd_link_hash_traverse
  PARAMS ((struct bfd_link_hash_table *,
           boolean (*) (struct bfd_link_hash_entry *, PTR),
           PTR));

/* Add an entry to the undefs list.  */
extern void bfd_link_add_undef
  PARAMS ((struct bfd_link_hash_table *, struct bfd_link_hash_entry *));


/* This structure holds all the information needed to communicate
   between BFD and the linker when doing a link.  */

struct bfd_link_info
{
  /* Function callbacks.  */
  const struct bfd_link_callbacks *callbacks;
  /* true if BFD should generate a relocateable object file.  */
  boolean relocateable;
  /* true if BFD should generate relocation information in the final executable.  */
  boolean emitrelocations;
  /* true if BFD should generate a "task linked" object file,
     similar to relocatable but also with globals converted to statics. */
  boolean task_link;
  /* true if BFD should generate a shared object.  */
  boolean shared;
  /* true if BFD should pre-bind symbols in a shared object.  */
  boolean symbolic;
  /* true if shared objects should be linked directly, not shared.  */
  boolean static_link;
  /* true if the output file should be in a traditional format.  This
     is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
     on the output file, but may be checked when reading the input
     files.  */
  boolean traditional_format;
  /* true if we want to produced optimized output files.  This might
     need much more time and therefore must be explicitly selected.  */
  boolean optimize;
  /* true if BFD should generate errors for undefined symbols
     even if generating a shared object.  */
  boolean no_undefined;
  /* true if BFD should allow undefined symbols in shared objects even
     when no_undefined is set to disallow undefined symbols.  The net
     result will be that undefined symbols in regular objects will
     still trigger an error, but undefined symbols in shared objects
     will be ignored.  The implementation of no_undefined makes the
     assumption that the runtime linker will choke on undefined
     symbols.  However there is at least one system (BeOS) where
     undefined symbols in shared libraries is normal since the kernel
     patches them at load time to select which function is most
     appropriate for the current architecture.  I.E. dynamically
     select an appropriate memset function.  Apparently it is also
     normal for HPPA shared libraries to have undefined symbols.  */
  boolean allow_shlib_undefined;
  /* Which symbols to strip.  */
  enum bfd_link_strip strip;
  /* Which local symbols to discard.  */
  enum bfd_link_discard discard;
  /* true if symbols should be retained in memory, false if they
     should be freed and reread.  */
  boolean keep_memory;
  /* The list of input BFD's involved in the link.  These are chained
     together via the link_next field.  */
  bfd *input_bfds;
  /* If a symbol should be created for each input BFD, this is section
     where those symbols should be placed.  It must be a section in
     the output BFD.  It may be NULL, in which case no such symbols
     will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
     linker command language.  */
  asection *create_object_symbols_section;
  /* Hash table handled by BFD.  */
  struct bfd_link_hash_table *hash;
  /* Hash table of symbols to keep.  This is NULL unless strip is
     strip_some.  */
  struct bfd_hash_table *keep_hash;
  /* true if every symbol should be reported back via the notice
     callback.  */
  boolean notice_all;
  /* Hash table of symbols to report back via the notice callback.  If
     this is NULL, and notice_all is false, then no symbols are
     reported back.  */
  struct bfd_hash_table *notice_hash;
  /* Hash table of symbols which are being wrapped (the --wrap linker
     option).  If this is NULL, no symbols are being wrapped.  */
  struct bfd_hash_table *wrap_hash;
  /* If a base output file is wanted, then this points to it */
  PTR base_file;

  /* If non-zero, specifies that branches which are problematic for the
  MPC860 C0 (or earlier) should be checked for and modified.  It gives the
  number of bytes that should be checked at the end of each text page. */
  int mpc860c0;

  /* The function to call when the executable or shared object is
     loaded.  */
  const char *init_function;
  /* The function to call when the executable or shared object is
     unloaded.  */
  const char *fini_function;

  /* true if the new ELF dynamic tags are enabled. */ 
  boolean new_dtags;

  /* May be used to set DT_FLAGS for ELF. */
  bfd_vma flags;

  /* May be used to set DT_FLAGS_1 for ELF. */
  bfd_vma flags_1;
};

/* This structures holds a set of callback functions.  These are
   called by the BFD linker routines.  The first argument to each
   callback function is the bfd_link_info structure being used.  Each
   function returns a boolean value.  If the function returns false,
   then the BFD function which called it will return with a failure
   indication.  */

struct bfd_link_callbacks
{
  /* A function which is called when an object is added from an
     archive.  ABFD is the archive element being added.  NAME is the
     name of the symbol which caused the archive element to be pulled
     in.  */
  boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
                                          bfd *abfd,
                                          const char *name));
  /* A function which is called when a symbol is found with multiple
     definitions.  NAME is the symbol which is defined multiple times.
     OBFD is the old BFD, OSEC is the old section, OVAL is the old
     value, NBFD is the new BFD, NSEC is the new section, and NVAL is
     the new value.  OBFD may be NULL.  OSEC and NSEC may be
     bfd_com_section or bfd_ind_section.  */
  boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
                                          const char *name,
                                          bfd *obfd,
                                          asection *osec,
                                          bfd_vma oval,